The present invention relates to the art of electric motors and more particularly to systems and methods for detecting motor faults by space vector angular fluctuation.
Many industrial processes and machines are controlled and/or powered by electric motors. Such processes and machines include pumps providing fluid transport for chemical and other processes, fans, conveyor systems, compressors, gear boxes, motion control devices, screw pumps, and mixers, as well as hydraulic and pneumatic machines driven by motors. Such motors are combined with other system components, such as valves, pumps, conveyor rollers, fans, compressors, gearboxes, and the like, as well as with appropriate motor drives, to form industrial machines and actuators. For example, an electric motor may be combined with a motor drive providing electrical power to the motor, as well as with a pump, whereby the motor rotates the pump shaft to create a controllable pumping system.
Motors, pumps and bearings require frequent maintenance and observation in typical commercial systems and industrial plants. Motor faults developed in critical equipment are commonly detected by human experts through physical examination and other off-line tests. Such motor fault detection may be performed during regularly scheduled maintenance, at which time corrective action may be taken according to detected motor faults or problems. However, faults that go undetected during or between such routine maintenance may lead to catastrophic failure and/or unscheduled downtime in a plant. The probability of such downtime increases as the time period between successive maintenance inspections increases.
The frequency of performing maintenance, however, is limited by availability of manpower and financial resources, and hence is not easily increased. Some types of motor inspections, moreover, require stopping the process or even disassembling machinery. In such cases, the lost production-time may cost significantly more than the inspection labor cost. There is also a possibility that the reassembled machine may fail due to an assembly error or high start up stresses, for example. Finally, periodically replacing motors and components thereof (via routine preventive maintenance) is costly since the service life of good components may unnecessarily be cut short. Thus, there is a need for systems and methods of providing motor diagnostics by which motor faults in motorized systems and machines may be timely detected, and which reduce or eliminate system downtime and the costs associated with human inspection and diagnosis.
The following presents a simplified summary of the invention in order to provide a basic understanding of one or more aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention, nor to delineate the scope of the present invention. Rather, the sole purpose of this summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented hereinafter. The invention provides systems and methodologies for detecting motor faults by space vector angular fluctuation, which require no human intervention or downtime, in order to identify motor faults such as stator faults, rotor faults, and even imbalances in power applied to the motor in a timely fashion. Systems and methodologies are provided for detecting faults and adverse conditions associated with electric motors. The methodology provides for analyzing the angular fluctuation in a current space vector in order to detect one or more faults associated with the motor. Systems are disclosed having a diagnostics component adapted to obtain a space vector from a current signal relating to operation of the motor, and to analyze the space vector angular fluctuation in order to detect motor faults.
According to one aspect of the invention, a method is provided for detecting motor faults, comprising calculating a space vector from a current signal related to operation of the motor and determining a space vector angular fluctuation. The space vector angular fluctuation may then be analyzed in order to detect at least one fault associated with the motor. The analysis of the space vector angular fluctuation may involve computing a frequency spectrum of the space vector angular fluctuation and analyzing the amplitude of one or more spectral components at certain frequencies. For example, fluctuations in amplitude of such spectral components may be analyzed or monitored in order to detect motor faults such as stator faults, rotor faults, shaft misalignment faults, and/or an imbalance in the power applied to the motor. Certain frequencies of interest may be thus analyzed, such as frequencies approximately twice the frequency of power applied to the motor. In this regard, a Goertzel algorithm may be advantageously employed to extract information related to certain frequencies of interest, in accordance with the invention.
Another aspect of the invention relates to systems and apparatus for detecting motor faults. Such systems may comprise a diagnostic component which obtains a space vector angular fluctuation from motor current signals, and which analyzes the space vector angular fluctuation in order to detect one or more faults in the motor. For instance, the diagnostic component may obtain a current signal associated with the motor, calculate a space vector from the current signal, and determine a space vector angular fluctuation from the space vector. The diagnostic component then analyzes the space vector angular fluctuation in order to detect at least one fault associated with the motor.